>I have a Dentron MLA2500 that has burped. It appears that the
>transformer is bad. If I attach the electrolytic capacitors and diode
>bank to the transformer it will pop the fuse. If I disconnect all from
>the xfmr it will not pop a fuse.
The transformer alone would blow fuses if it had a short.
> In the past, I replaced the diodes and
>electrolytics becuase the others were original and one cap had been
>replaced by the original owner. Most of the xfmrs I have seen go bad
>in the past have been dead shorts. Is it common for a transformer to
>be bad when under a small load? It appears that just the surge of
>charging
>the caps does it. It does put out voltage as shown on the meter until
>the
>fuse pops. Of course I hve taken the tubes out of the picture by
>disconnecting them. What is a good way to test the xfmr ?
>
Operate it with nothing connected to the secondary and measure the
primary current. If the primary current is under 1A, (or it doesn't blow
fuses) the xfmr is not shorted. When replacing rectifiers, 'tis best to
eliminate "equalizer" R/C networks. Digi-key sells a Panasonic
(Matsushita) 500V electrolytic that are a suitable replacement for the HV
filter caps. They also sell Panasonic 3W, 100k-ohm resistors that are
reliable 500v electrolytic-cap bleeder/V-equalizer resistors. If the
transformer proves to be bad, please let me know. tnx
cheers, Doug
- Rich..., 805.386.3734, www.vcnet.com/measures.
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